Abstract The 2000 Surgeon General's Report on Oral Health identified the relationship between improvement in periodontal health and glycemic control as an area in need of intervention studies. To date there has been no adequately powered clinical trial to address this question. The proposed Diabetes and Periodontics Trial (DPT) is a multi-center, randomized, controlled single-masked Phase III clinical trial designed to test whether non-surgical periodontal therapy (scaling and root planing) is effective in reducing HbA1c of patients with type 2 diabetes and untreated chronic periodontitis compared to a control group who will receive no initial treatment. Delayed treatment will be offered to the control group after the 6-month visit. The secondary aims will evaluate whether improvement in clinical measures of chronic periodontitis are related to changes in systemic inflammatory markers, HbA1c, and measures of insulin resistance in these patients. Over a two and a half year period, four Clinical Centers from Schools of Medicine and Dentistry in Birmingham, AL, Philadelphia, PA, San Antonio, TX, and Minneapolis, MN will recruit a total of 600 adults (150/center) 35 years of age or older, with type 2 diabetes of at least 3 months duration, untreated moderate to severe chronic periodontitis, HbA1c between 7.5% and 9%, and who meet additional specific inclusion and exclusion criteria. Subjects will be recruited from the diabetes clinics, dental clinics and communities at each center. All eligible subjects will be examined at baseline, 3- months, and 6-months; at each visit a periodontal examination will be conducted and HbA1c values determined. Treatment will consist of scaling and root planing under local anesthetic. A standardized common protocol, and a detailed Manual of Procedures will be used at all centers. The primary study outcome will be change in HbA1c values at 6-months. Secondary outcomes are changes in periodontal clinical measures (gingival index, bleeding on probing, pocket depths, and clinical attachment levels), changes in inflammatory markers (serum C-reactive protein, plasma TNF, and serum IL-6) and changes in the Homeostasis Model Assessment (HOMA2). This study has the potential to provide a scientific basis for an improvement in the standard of care for patients with diabetes thus addressing one of the Public Health Service's Healthy People 2010 goals. This application seeks support for the Administrative Center/Study Chair. Separate applications have been submitted by the Coordinating Center, and four Clinical Centers. Project Narrative Having periodontal (gum) disease may make it more difficult to control blood sugar levels for people with type 2 diabetes. This study will test whether non-surgical periodontal disease treatment leads to improved blood sugar control. Improving the way people manage their blood sugar is key to preventing diabetes complications and reducing health care costs.